To me, it seems like "killed" is a synonym for "devastated" in this case. The first part is Deidre telling Drake that his acting in the scenes that they taped that day "killed" (devastated) her. The second part is Marlena telling John that what he did in those scenes "killed" (devastated) her.

But I could be wrong.

So is John going to come across looking like an even bigger, unsympathetic, non-heroic asshole than he already has?

This is my theory and I'm sticking to it.

J&M are actually working with each other but no one else knows this. Maybe John "kills" Marlena or makes it appear he has.

Drake could have been making D laugh....."You kill me" hahaha type of thing.